<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        div{
            width:300px;
            height:300px;
            background:#fff;
            box-shadow:0 0 30px rgba(0,0,0,.2) inset,0 0 4px rgba(0,0,0,.2);
            margin:50px auto;
            text-align:center;
            line-height:300px;
            position:relative;
        }
        div:after{
            content:'';
            display:block;
            width:150px;
            height:30px;
            position:absolute;
            left:4px;
            bottom:5px;
            box-shadow:0 4px 6px rgba(0,0,0,.8);
            background:#fff;
            transform:rotate(-4deg) skew(-15deg);
            z-index:-1;
        }
        div:before{
            content:'';
            display:block;
            width:150px;
            height:30px;
            position:absolute;
            right:4px;
            bottom:5px;
            box-shadow:0 4px 6px rgba(0,0,0,.8);
            background:#fff;
            transform:rotate(4deg) skew(15deg);
            z-index:-1;
        }
    </style>
</head>
<body>
    <div>翘边阴影</div>
</body>
</html>
